Thanks for the response, I appreciate any feedback. I should have been more clear: the old pilot jet was seized and I drilled it and used a file to remove it. Then I put a new stock one in and it snuggled up nicely in place.

Just picked up a 1990 dr250 with 11,000 miles on the odometer. The guy I got it from had it sitting in storage since 2008. It looks great. Clean motor and plastics, no missing mirrors or blinkers, and flawless stock seat cover. Having sat for 10 years I opened up the carb and ordered a rebuild kit. The o-rings were in rough shape and the float needle’s spring was seized. Had to drill out the pilot jet. Anyway, I installed a new pilot jet, gasket/o-rings, and needle and seat. Disassembled the choke plunger and cleaned it out to ensure it was clear of debris. Thoroughly cleaned all passages I could see with carb cleaner, compressed air, and wire. With stars in my eyes I put the carb back on and the bike started first couple of kicks and idled well, but I had to have the idle screw just about all the way in. I hopped on and went for a brief ride down the road. Within 30 seconds it started running rough and stalled. I got it going again and headed back to the house. At this point the bike refused to idle and sputtered pretty badly through the rpm range. I pulled the plug and it looked like garbage (old and black) so I gapped a new one and put it in. I also pulled off the tappet covers and checked the valve clearances. Based on my inspection all 4 were in spec. At some point I went to start it again and it fired up and ran well for a few seconds, then started to struggle again. After it died I kicked 8-9 times with no hint of a start. I pulled the new plug and it was soaked. I experimented with the mixture screw and tried running the bike with the screw turned 0 to 4 turns out at several intervals with minimal luck. During this entire time I’ve had the air filter off, so I’m sure it’s not suffocating from any lack of air. Any ideas? I’m trying to stay level-headed but I just might donkey-kick this thing if I can’t make any progress!

My apologies if the title smells clickbaity! I suppose I could have said “Is buying a new bike a very bad idea financially?” I agree with the high maintenance costs. With my latest bike I’ve chucked around $500 at it just this summer to keep it in good shape.

I've had a few different dirt bikes in past years that were aged enough that I was able to sell them for close to the same price I bought them for. Because of this, I've enjoyed the ability to ride on what basically feels like free/cheap bikes. There are drawbacks, of course. It's always scary buying a machine that has had several owners, which means its history is vague. Unexpected parts break down at unexpected times, and I suppose I've rarely experienced pure peace of mind because of that.
The alternative to my past method which would provide peace of mind and fewer breakdowns is to buy a brand new bike or at least one that is newer than a couple years old. The bummer in that case however is that the bike would lose much more of its value and mean that I would sell it at a great loss. Or am I wrong? I'm not looking for those "well it's an expensive sport so buck up" comments. I'm genuinely curious about what seems like a financially smart move to you guys. Buy new and keep the bike for a decade? Buy older bikes and swap them out often? I often wonder what the prime ownership strategy is in order to keep money expenditures low and bike quality high.
I'm not very hardcore. Just a weekend rider type who enjoys semi-vigorous trail riding. No racing. What are your thoughts?